Get the deep 1 gallon pots. They are not very wide so they can be packed close together, but still allow a good bit of roots. technically roots like to spread out, and often do not use much of the middle of the pot, but for that small I doubt youll run into much of a rootbound issue. Have you considered a planter box instead?

A planter box can be very shallow, 5-6" deep, whatever width and length you want. This is really all they need, because they have tons and tons of space to spread out amongst eachother. You can pack a lot of plants close together this way. Just make sure its all the same strain (and preferably the same mother) so you get more uniform growth.